1. Field of the invention
This invention relates to warning signals, and particularly signals for use on railroad locomotives.
2. Description of the Prior Art
To warn pedestrian and vehicular traffic of the approach of a locomotive at a railroad grade crossing, safety regulations have been established with respect to the operation of the locomotive. Present laws require the train operator or engineer when approaching a crossing to illuminate the locomotive headlamp, to ring the bell, and to sound the horn or whistle in a prescribed form. To further warn crossing traffic, road crossings also often have on-site protective devices such as cross-arms, stop lights, red signal lamps, and gates. The effectiveness of these warning devices is vital, since heavy freight or passenger trains traveling at track speed usually cannot be brought to a stop in time to avoid a collision with a vehicle or person who has not observed the existing signals and warnings.
In many cases, the existing warning signals are inadequate. Statistics published by the U.S. Government, Department of Transportation, Federal Railroad Administration show that approximately 1500 to 1800 people are killed and between 3800 and 4000 are injured each year at railroad grade crossings. These accident rates have remained fairly constant over the last few years while train traffic has declined and vehicular traffic has increased.
In an attempt to provide pedestrian and vehicular traffic with a better warning of the approach of a locomotive, additional signal lights have heretofore been placed on locomotives. Typically, such warning lights mounted on the front of locomotives have included mechanical apparatus for providing lateral movement to the lights or to oscillate the lights to increase the effect of the warning signal. However, it has been inherently expensive to manufacture such devices because of the intricate relationship between the various components and the need for a motorized source of power to drive the apparatus which moves the light in the desired pattern. In addition, the various components required precise assembly and adjustment to assure that the desired pattern of the light beam would be established at the proper range and position in the path of the locomotive.
More recently, the mechanized devices have been replaced by electronic circuitry which turns the warning lights on and off. Examples of such electronic systems are shown in U.S. Pat. No. 3,113,293 issued to R. F. Breese et al., and U.S. Pat. No. 3,908,179 issued to A. C. Heehler et al. The electronic circuitry in these devices, however, comprised simple on-off devices which alternately supply power to the light and deactuate the light to produce a flashing effect.
With all of the prior art visual warning signals for locomotives, the effectiveness of the signal has been limited by the brightness of the lamp. With mechanically or electrically oscillating signals, the distance over which the signal was effective has depended upon the relative strength of the lamp, and this, in turn, has been limited by the amount of power supplied to the lamp by the locomotive electrical system. An extremely bright lamp has been impractical since it would produce an extremely large drain on a locomotive electrical power supply.
In addition any such warning signal is, of course, completely ineffective if it is not used. The continual flashing of a warning light on the locomotive is extremely distracting to the locomotive operator or engineer. Therefore, any such signal must be actuated each time the locomotive approaches a grade crossing. However, if the operator or engineer neglects to actuate the signal, any benefit of such a signal is lost.